Three people died in a shooting at a large shopping centre outside of Baltimore, Maryland, today , and one of the dead was believed to be the shooter, police said.

Police said they were allowing shoppers to leave the Mall in Columbia, in Columbia, Maryland, after determining there was no longer a threat, Howard County Police said on Twitter.

Police said they did not immediately know the identities of the dead.

Police said a 911 call at about 11:15am (4.15pm GMT) reported that shots had been fired at the mall, a sprawling shopping centre with about 200 stores about 48 km north of Washington, DC.

Colin Reddy, who works at the mall, told CNN he “heard a loud boom.” “We thought it was construction because there’s a lot of construction going on at the mall right now. Then I heard it again. Like ‘boom, boom, boom’. And then everybody started running,” he said.